if(nomjours<=3)
{
alert("you select a day between 1 to 3");
}
else if(nomjours>3&&nomjours<=6)
{
alert("you select a day between 4 to 6");
}
else if(nomjours>6&&nomjours<=13)
{
alert("you select a day between 7 to 13");
}
else if(nomjours>13&&nomjours<=20)
{
alert("you select a day between 14 to 20");
}
else
{
alert("you select a day more then 20");
}